A Brooklyn teen found a modern solution to an old-fashioned crime – she tracked down her cellphone mugger using MySpace, police said.

“He came from behind and snatched the phone from me – I chased him but I couldn’t catch up,” Yudelka Polanco, 16, told The Post.

It was 8:30 p.m. on a freezing Jan. 26. Polanco was tired, just coming home from a guitar lesson, and was carrying a large bookbag on Hooper and Hewes streets in Williamsburg. She had no chance of catching the young thief.

But although the Bushwick teen couldn’t physically run down her assailant, she was able to follow his electronic footprints.

About two weeks later, when she received the replacement to her stolen T-Mobile Sidekick Slide, one of the first messages she received revealed her attacker’s e-mail address.

“He had signed on to his e-mail with my SIM [subscriber identity module] card still in the phone,” said Polanco.

She turned on her computer and began her detective work.

“I put his e-mail address into MySpace – because nowadays everybody has MySpace,” she said.

“I found his picture, but it was a picture of him from the side, and I wanted police to have something better.”

So Polanco actually got another cute gal pal to start an online friendship with the mugger – who cops say is Victor Hernandez, 16. The friend was able to collect more pictures and information on him.

Having done most of the investigative work, Polanco went to cops with a plethora of pictures of the thug.

Then, based on of the information on his MySpace page, cops surmised that Hernandez was in a local gang called “DPL.”

Cops eventually were able to find Hernandez and hauled him into the 90th Precinct station house Monday for questioning, law-enforcement sources said.

Polanco was able to pick him out of a lineup and Hernandez was arrested for menacing, grand larceny, robbery, possession of stolen property and harassment.

Cops also hooked Hernandez in another wild incident Jan. 30 on the mean streets of Williamsburg.

Police sources said Hernandez was one of 20 people who congregated in front of SeÑor Taco restaurant on Havermeyer Street with machetes, metal bats, canes and glass bottles.

The mob attacked two brothers, ages 18 and 20, who worked at the restaurant, slicing one in the back.